I'm very sorry your experience was less than magical. However, I'm trying to understand a few things.
1) Did you not have a handicap placard for your car? If you don't have one, then the CM was correct in telling you your car could be towed if you parked in a handicapped space. That's the law. A note from a doctor isn't sufficient. You perceived the CM as "threatening" to have your car towed, but he would have been simply doing his job which is to make sure that the cars parked in the handicapped spaces have the appropriate placards or plates that indicate they are allowed there.
2) Did you research ahead of time what rides would necessitate a transfer? There's tons of information here and at allears.net, as well as in guidebooks, that you might have found helpful in preparing you for touring the parks with a disability. A stop at Guest Services could have also been helpful because they can provide you with a pamphlet that could have assisted you in knowing which rides would be more accomodating. A trip to Disney parks goes more smoothly with research and planning, whether the guest is disabled or not.
3) You really tried to get to all 4 major parks in one day?
As an adult without disabilities, I wouldn't be able to enjoy myself if I was so rushed to make it to all 4 parks in one day. I have a special needs daughter, and there's no way I could press her to do 4 parks in one day without it being a complete disaster.
4) The fact that Via Napoli stops seating at 8:30 is in no way connected to your having a disability or not. Again, a little research ahead of time would have been helpful. And I'm not sure why you still left rather than staying to watch Illuminations. If you had gotten seated at Via Napoli at 8:30, you would have missed Illuminations anyway. Since you didn't get seated, why not stop and see the show that you had been looking forward to?
I wish I could feel more sympathetic to your situation, but it seems there were many things that you want to blame Disney for that were within your own control.